Signaling system



Aug. 22, 1933. L. A. GEBHARD SIGNALING SYSTEM Filed May 29, 1930 2 Sheets-Sheet l INVENTOR. 9226645146,

A TTORNEY Aug. 22, 1933 L, A. GEBHARD SIGNALING SYSTEM Filed May 29, 1930 2 Sheets-Sheet 2 I I I I I I I I I I I I l I I l I I I I I l I I I I I I I I I I I I l I I I l I I I I I I l I I INVENTOR. Q0/1423 a swxgma,

A TTOR ;/EY

system and the radiating system.

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I g 1,923,295 v V srcnsicrnasrs'raivi K Lewis A. Gebhard, -Washington, D. assignorl] to Wired Radio, line, New York, N. Y., a Corporation oi Deiaware L P Application May 29, 1930. Serial No. 457,445

' t a ing; ((11. 250 -17) My invention relates broadly to high frequency trol circuit for a transmitter wherein electrical. signalingsystenis and m'ore specifically'toa radio oscillations generated by an electron discharge 7 frequency feed circuit in high frequency signaling device, having associ'atedtherein a frequency stasystems of large power output. lbilizing and controlling element of the piezo elecan arrangement in a high frequency signaling pressedupon the circuits or frequency multiplyystem perative Over number'oi different ireand power amplifying electron discharge dequency channels with means for accurately advices, which'are preferably of the shield grid justing the coupling between the power amplifier type. 'In a radio transmitter operating over a wide band'of frequencies a very flexible coupling Another-object of my invention is to provide a" system must be used. This is particularly true transmission circuit arrangement including a, where the operation is from a low power stage to high power symmetrical circuit section and .a low a high power stage employing water "cooled tubes power unsymmetrical circuit section with switchin a push-pull system.- This coupling system One of the objects of my invention is to provide tric crystal or magnetostriction type, are imiii? ing means for selectively controlling the connec-- vmust not only be flexible but it must beso 'detions between said sections with 'an' antenna signed as not todestroythe balance in the opsystem. r r eration of the tubes in the push-pull system. Another object of my invention is to provide a Any unbalanced distributed capacities tend to uncircuit arrangement for a signaling system adaptbalance the loads on the-tubes in the push-pull ed for high power operation on any one of a system. w l number of different frequency'channels in which In a high powertransniitter for high frequency a variable capacity element is interposed between signaling it is desirable to have the low power portions of the power amplifier systemfor regustages of the, transmitter constructed of the lating the coupling .between the several circuits single-ended or unsymmetrical type while of the transmitter. r 7

Still another object of my invention is .to pro constructed of the double-ended, push-pull or vide an arrangement'in a' signaling system em-- symmetrical type'for thevfollowing reasons: ploying electrondischarge devices of large power (a) When crystal control isvused in the. trans-I output by'whichsubstantially balanced'operationlmitter a push-pull circuit requires isolating of the high power electron dischargefdevices is from ground both sides .of:the.'crystal which are 5 obtained at high operating frequencies while .range nentdoesnotlend itself to accurate temmodification in coupling between 'the power perature controliand therefore the. accuracy of amplifier stages may be readily effected. frequency isimpaired. This isolation means that A furthe Obj t Of y invelltic-his to provide the lower plate of the crystal cannot be connected a fr qu n y control circuit f a signaling 'sys in common with the other'lower plates of other 66 employing a p W 037616013011 h fi e"crystals which -aregenerally placed on-alarge, d vices of large power Output in a fl fi Cirplate having good thermal.conductivitywhichpree- Quit arrangement W is adapted t0 Operate vents excessive temperature differences between readily many of a p1 alityoi frequency chancrystals. This permits changing frequency by, nels, and in which substantially balanced and changing from one crystal to another quickly and stable operaticn is obtained in the 'large power stillhave good accuracy with respect tan output electron discharge devices at high 010- quency, If 'a temperature control system having crating frequencies whilepermitting various de-- a number of crystals in a common plate is used in grees of coupling to be obtained between the p0W- a push-pull system then the circuit will not er'amplifier stages. w j have perfect symmetry. The common plate can- Othera'ndfurther objects of my invention will not be" grounded and it. will hav 1 1%? ca a y be apparent to those skilled in the art-to which to ground which does not exist on th e other this invention pertains from thefollow'ingspeci half of the circuit. The. common plate usually fication by reference to the accompanying. drawcarriesa thermometer'for indicating the 'tem- 5 9 ingsin which: 7 1 f perature, which in this case would be subjectfto ,liigureidiagrammatically shows thetransmita radio frequency potential resulting in heating ter-circuit arrangement m odying my invent-i oi the glass andtherefore cause'inaccuracies' of and Fig. 2shows certain details of the switching mc t, rfi o t3t1 t. on' 'ol 1 1 circuit illustratedin Fig. 1;. I side the common plate would also be subjectjto 1 'My invention is directed 'tofa frequency c011-."-thisina ccuracy whichis increased due to the fact" the high power section or final stage or stages are I 703 taking place in the circuits of the. electron disthat the mercury inside the thermostat is electri cally connectedto the temperature control and heater circuits which are substantially at ground potential of radio freduencies.

' (b) The changing of frequency of singlc-ended circuits is very much simpler and requires much less time than in the case of push-pull circuits;- This is true'for a crystal oscillators-ir cuit as well as a screen grid amplifier circuit employing screengrid tubes.

' (c) The construction of such circuits is simpler and the expense smaller and physical space o'ccupied less thus making for. greater compactness in the apparatus. it is much easier, simpler and cheaper and more compact to obtain. quick change between sin--' gling, doubling and tripling of frequency operations. I

(d) In the final stage or stages of the transmitterit is more desirable to use push-pull circuits-in that.three-element high power tubes are the only'ones generally available. The use ofthe push-pull circuit inherently, reduces difficulties experienced from harmonics.

improvedbalance of electric coupling on accountof. the inherent interelement capacities in the tubes; cuits enables thetransmitter to be operated at higher frequencies since the inter-electrode capacities between; the plate and filament as well asother stray capacitiesare in series instead of inparallel. In the circuits or stagesof the transmitter near the, oscillator :the inter-element capacities are notsufiiciently important as to overweigh-the other advantages of single-ende: cir- 'cuits because, first, the inter-element capacities.

are smaller which permit paralleling of tubes if necessaryato a limited degree, which may be re- "quired due to the lack of higher powered screen" grid-tubes; and still coverv frequency range, and

' second with the exception of. the last stage feedit the 2000-5000 kilocycl e' band and higheroutput that; single-ended circuits are better for earlier and; lower power circuits of 'a transmitter and push-pull) or double-ended circuits are bet- 605- V push- 101111 circuit.-

ing vinto the highpower amplifier input circuit, the earlier stages do not have to cover aswide a frequency band sincethe crystal is generally in frequencies are obtained by'doubling and tripling frequency operations. a From the above analysis it will be understood ter'for'the final and higher power circuits. .My

invention provides means for coupling the last unsymmetrical circuit of the line-up to the symmetrical'circuit' without interfering with the symmetry orgthef latter'cver a wide frequency band. The couplingprovided is flexible enough to cover all requirements for proper excitation of the I-n'the system embodied in my invention continuously variable inductance unitsfhaving'an "sumes a semiaperiodic character between cerarrangement associated therewith for varying the numberjof turns op'eratively'connected into circuit and for short circuiting the turns not in use, are emplcyed'for interstage coupling between the amplifying electron'discharge devices. The tendency forlintersta' ge self-excited oscillations charge deviceamplifying system is thus materially reducedtand theiiexibility'o'f the amplifier is increased since the f-requency characteristics of cachet the electron discharge device units as- In single-ended circuits.

Its use also *permits improved stability of an amplifier due to In-addition-the use of pushpull,cir-' 1 device 3.

is associated with the; cathode electrode of the electron discharge-device 3.

put circuitofthe power amplifier and the cou-' pling circuit to the inputof the push-pull amplifier. J Byadjusting this variable condenser I am enabled to control the coupling between the power amplifier and the push-pull amplifier within the limits of the particular coupling device which connects the output circuit of the power amplifier with the input circuit of the push-pull In Figure 1, reference numeral, 1 designates, a frequency controllingelement of the piezo electrical crystal type which is connected 'to the control electrode of' the electron discharge device 3. A choke coil 2 is connected betweenathecontrol electrode and the cathode of,.the electron discharge deviceS'. Anoscillatory circuit comprising the inductance 5 and the capacityfi is connected into the anode circuit of the device 3.

Radio frequency bypass condenser 6a is provided between the inductance 5 and the cathode of the A source 4 of: cathode heating current discharge device 9 of thescreen grid type is associated with the output circuit of the device 3. Electrical oscillations are impressed upon the grid electrode a of the device 9 from the oscillatory circuit 5-6, through condenser I. A resistance unit 11- is connected to'the screen grid electrode 12. An inductance 15 isconnected into the output circuit of the device 9. A variable contact 16 which is connected to the variable tap 16a on the inductance 15 is provided for varying theefiective number of turns of the inductance 15, that are-operatively connected into the output circuit of device 9. The turns of the inductance Y which are not operatively connected into circuit .are short circuited.- A radio frequency bypass condenser 17 is provided between the tap 16a on the inductance i5 and the cathode electrode of device 9. Electron discharge device 20 which is also preferably of the screen grid type, is connected with the output circuit of device 9] A capacity 19 is connected between the grid electrode d and the output circuit of device 9. A

' resistance unit 22 is connected to the shield grid electrode'e. An inductance 25 is connected to the anode electrode f of the electron discharge device 20.

A variable contact 26 is connected to the point 26a on the inductance 25 for varying the num- .ber of turns of the inductance that are operatively connected into the anode circuitof the device 20. Bypass condenser 23 is connected between the screen grid electrode c and the cathode of the electron discharge device 20. Another high-frequency oscillation bypass condenser 27 is' connected between the inductance 25 and the I cathode. Sources 10 and 21 are connected with A second electron Q."

the cathodes of electron discharge devices 9 and 20, respectively. An inductancev system 31 comp rislng the windings 32 and 32a, one of which is concentrically and symmetrically disposed trodes aand d of devices. '9iand'20,respectively.i

Connection 13a is 'providedfibetween a' variable.

t n V 1,923,305. within the other, isfernployed to couple the out put circuit of the' electron'dischargegdevice to the, input circuits of the electron discharge devices33 and 341which are connected in balanced circuit arrangement; The inductance sys tom 31 comprising the windings 32 and. 32a is preferably of a readily variable type having contacts 52 by. which-the'circuits are completed to:

the push-pull "amplifier circuits of tubes 33-,34.

The coils 32 and 32a have very small jcapacities between them and the magnetic coupling pre dominates over the electric coupling;- Independent contacts leading to the power supply circuit are associated with the contacts 52vinsuch,

manner thatthe circuit between these contacts 35 is broken before the inductance. circuits at; contacts 52 are broken and establishedafter the inductance circuitsatcontacts 52 are established.

in order to prevent: disastrous effects of opening the inductance circuits while radio frequency oscillations of large ainplitude-'ar;present therein. Relays 14, l4ag 2 l andv29; which are connected 'to the source of power supply .30 and'the" contacts 35 are employed for controlling the connections to the sources of power supply 13, l3a and 13b which may be of any approved type, such as a battery, motor generator systein or rectifier1 connected to. an alternating current supply system. i A.

The negative terminal of the source l3isrpref-. erably connected to the choke coils 8'and 18 through a resistance unit 130, forimpressing negative biasing' pote'ntial upon the grid .electap on resistance unit-13c, which is connected across the source .3 and the common cathode connection of devices 9 and 20. Relay l ia is provided to complete the connection from tap 13d to the grids of tubes9 and 20.-v The resists.

ance, units lland 22 and the inductanceunits 5, 15 and 25 are connectedtogether to thepositive terminal or" the source 13a. The value of the resistance units 11am 22 'must be carefully chosen in order that the proper potential is-inn,

- pressed upon the'screen grid electrodes b and e of the devices' 9 and 20." Where it is desired the resistance units 11 and 22 may be eliminated and connections between the:. screen grid electrodesib and e and the proper points or" theresistance 13f', which is connected acrosspthe source of supplya1-3a made directly. vRelay 24 is employed to coinplete theplatefand shield-grid circuit connections toavther-v positive terminal of the source'of supply'zltiae When the circuit ofv relay '24 isbroken the 'anodercircuits of the electroirdischar'ge devices 9 and 20 :are deenergized andthe circuit between the source 13a and the shield gridflelectrodes b and e is interrupted.- 1 Relay 29 is connected to the 'positive terminal.

of the source of supply 1% to control the energization of ,the anode circuits of electron discharge-devices 33 and'3 l. A source .of cathode heating current 42is' provided for the electron discharge devices 33 and 34.

In a highfpowe r, transmitterit is desirable to r be able to cut. off thefinal high power circuit anduse the power in the circuitjust previous,

for output in thejantenna Fullflpower is;not required under' all conditions of transmissioniso this feature in the transmitter of any-(invention V, Fperrnitsgreat-economy. Again if somepart in the high power circuit, shouldffail in theemergencyv the "lowenpower circuit could be .used;

The higher power circuit can be isolated so that it is possible repair it eveniwiththe low powor section in operation, Suitable switches may be provided to out off the supply sources 7 to the high power section to permit repairs thereon. In order to provide for this. operation'the coupling system between last, unsymmetrical circuit and final symmetrica circuitmust be arranged so that in additionto aforesaid coupling requirements proper antenna coupling facilities may be'provided.- 1

' Variable condenser 28 is connected between the output circuit. of device-20 and the inductance Silafor varying the coupling between the'outp'ut' circuit of the device and the balanced input ci cuit ci'vthedevices 33 and 34; By adjusting variablecondenser 28 variousfldegrees' of coupling f between-amplifier 20 andpush-pull amplifiers 33 and 34 are obtained; This adjustment, however,

is limited by'the" range of the coupling between coils ,32aafand 32.; if it is desired to extend this range beyond the-po nt afforded by condenser 28 andwhen the frequency 'is' carried beyond the limits'of the combination oficoil 32 and con-' densers36 and 36a, coils 32aand 32 may be changed so as tobe either larger or smaller as required." Thecontacts 52 are provided .so 'that J the coils 32a and 32' may be arrangedina single unit and-quicklyinterchangeable. IVariable capacities 36c 36 are connected in series across the winding 32 oi the inductance system 31.

Variable condensers 37 and138 are'connected betweenithe winding 32and the anode electrodes of electron discharge devices 33zand 34, respectively, for neutralizing the effect of the interelectrode capacities of the electron discharge devices.

33-and 34." The electrostatic capacities 45,. i6,vv

3'7 and. 38 are preferably of the type disclosed in my-copending application Serial No. 327,990 for Condenser systems, filed December 22;

1928. Connections are provided between the capacity 3'? and the grid electrode of the electrondischarge the electron discharge 33. Substantially balanced operation is thus obtained in ,thecircuits device 34; Similar connections are'provided'between the capacity 38 and the-grid electrode of of the circuits of the electron dischargedevices 33 and 64., The loads taken by each of the elec-. q

tron discharge devices may thus be made equal ,in 'rnagnitude.- This is-highly desirable in the operation of high-power systems of this character since the possibility of the occurrence of disasunbalanced circuit operation is practically eliminated. g Y a The source 13 of grid electrode biasing potential iorthe electron discharge devices 33 and 34 is connected to the approximate electrical center of, the inductance 32 through the chokecoil 39. A high frequency oscillation bypass condenser 41 is connected across thechoke coil 39 and the ,trouseffects caused by overloading by reason of source 13. An inductance 47 is connectedibetweenvtheianode electrodes of the electron discharge devices 33 and 3e. The electrical center or approximate electrical'center of the inductance 47'is connectedcto the cathodes of the devices v and 34; through the chokecoil i4 and theconthe inductance i'l and forman-oscfllatdry circuit, in combination therewith.- Condensers 48 and l9 1 are; connected into the; high frequency transmis-- f si'on line 51 which is connected to the inductance 47-for energizing the antenna-doublet 50. Con-.

tacts 53 may be made 'to inductance 4'7 in such mannerthat an inductance unit of different frequency'range may be readily substituted for the inductance shown when the transmitter is to be adjusted outside of the range of any particular nductance." i I 1 In Fig. 2, I have shown an enlarged detailed wiring diagram of the transmitter circuit, in

which theantenna, characteristics may be changed with a change in coupling. A- plurality of simultaneouslyoperative switch members 101 102 and'103 are provided each movable over a setv of contacts under control of; manual adjustment device 105 .andgearing 104 in opposite directions as shcWngThatis to say, switch 101 is. driven over contacts a, b, c, d anda, b; c and d a in one direction while switches 103 and 102 are driven over contacts a, 1)", cf, d:and ar",

12, d, and c in the opposite direction. Quick. shift switches 101, 103, 102 may. be provided so that the proper antenna coupling system may be selected and sothat coupling of the lowpower unit may be shifted from the high power section %'to the antenna 'circuit, and the high power unit 'may be connected and disconnected. from the antennarespectively... When the low power section is used on the antenna the doublet is arranged as a '1 type antenna and .when the high power section is use'dthe antenna .is used as a'doublet systern with its advantages for high power opera.-

tiOH-w Switch 101 is located in the low power section of 'the transmitter and .switches'102'and 103 arelocated in the high power'section ofthe transmitter. The contacts ofswitch 101 connect as shown. That is contact 11 connects to the end of the inductance32a while contacts 0 and 1: connect to the end of the auxiliary inductance 25a as shown. The turns of inductance 25a'are selectively fixedby the movement of contact member 2519; The contact a in the lower group of contacts is leftfree. In the upper group of conthat the push-pull amplifier is arranged in the high power section in the manner set forth in tacts a and b are' connected together and connect through lead 55 with contactsa", b", c"'of switch 103 and a b" ,lc of switch 102, as

shown. Contact "0' of switch 101 isconnected in series through lead 55 through condenser 28a.

Contact d is left free; The high power section of the transmitter has been illustrated in a fragmentary manner in-Fig. 2 itbeing understood Fig. 1, the output of the push-pull amplifier including inductance 47. The coupling condensers 48 and 49' however, instead of connecting directly to the doublet 50 extend to contacts d and d' over which the'switches 103 and 102 sweep in interlocked relationship with the movement of switch 101. By the switchingarrangement illus trated the doublet antenna 50 may be changed 'into'a 'simple'T antenna and connected directly transmitter on low power without operation of the high power unit under conditions where it is unnecessary to radiate excessive power or where,

breakdown occurs in the high power unit. Various positions of switch 101 on contacts a; b; and

0, give different combinations of antenna coupling" and tuning with the 'aid of auxiliary inductances 25d and condenser 28a. In the positiona of switch'101, only the condenser 28' is in circuit and the antenna is simply capacitatively' coupled v to thelowpower unit. Thus condenser 28 may perform the' function of coupling the set to the antenna when switch l01is in position a,'b or 0 while condenser 28 serves to couple the low'power.

section to the high power section when switch 101 is in position d. I may providefswitchesfcoor dinated with the movement of switches 101, 102 and 103 for cutting off the plate voltage to the high powered tubes 33 and 34 and opening the filament circuits to these tubes when the switches are on positions a, b or c. In this way the high a power section rendered ineffective when the low' powersunit is used'alone. In the position d for with. the circuit explained in connection with Fig.

1. The arrangement of the other parts of the circuit supplementary to those illustrated in Fig.

1 enable the system to be moreeifectively utilized for the control of coupling, thedesired characteristics of the antenna used vwith the transmitter, and it enables thepower which is radiated to be more definitely selected.

I The system of 'my invention has'proven highly effective in operation. 4,000 to 21,000 kilocycles has been successfully covered and a smooth variation of coupling obtained throughout the range. The coupling between the output of the power amplifier 20 and the input of the push-pull amplifiers 33-3 lis wholly controlled throughout theftuning range or period of the coupling transformer 31 by micrometer adjustments of the variable condenser While I have described my invention in a certain preferred embodiment it .is understood that modifications thereof'may be made without departingfrom the spirit of my invention and that therefore I do not desire to confine my invention to the exact details as described except insofar as'these details are defined by the appended claims.

, What I claim as new and desire to secure by A frequency band of Letters Patent of the United States is as follows: 7

1. A signal transmission system comprising in combination a source of substantially constant frequency oscillationsyan amplifying system for increasing the amplitude of said oscillations, a

pair of electron discharge devicesconnected into a balanced circuit arrangement, and means coupling the output circuit of said first 'mentioned amplifying system with the input circuits of said pair of electron. discharge devices comprising a variable impedance device, an ouput circuit connected with said-pair of electron 'discharge devices, a radiating j system connectible .With said output circuit, and switching means. for selectively connecting 'said first mentionedamplifying system directly with said radiating system or through the circuits of said pair of electron discharge devices and simultaneously changing the transmission characteristics of said radiating system. t I r 2. A signal transmission system comprising in a pair vof electron discharge devices of large metrical circuit arrangement, a variable impedance element for, selectively coupling the output 1 power output connected into a substantiallysym circuit of said amplifying system'and the input circuit of said ,pair'of electron discharge devices, anoscillatory circuit connected to the output electrodes of said electron discharge devices, an antenna system, and means connected between said antenna system, the output circuit of said electron discharge devices and the output circuit of said amplifying system for controlling the transfer of high frequency energy to said-antenna system directly from the output of said amplifying system or through said pair of electron. oischarge devices and selectively fixing the trans mission characteristics of said antenna system;

. 3. A'sign'al' transmission system comprising in combination, a source of subsiai *ally con L- frequency oscillations, a first amplifier for increasing the amplitude of 1 cscillations a second amplifier comprising a pair of electron discharge devices connected into a substantially symetrical circuit arrangement, a variable condenser disposed between the output circuit of the first-amplifier and the input circuit of the second amplifier for controlling the coupling therebetween', circuits interconnecting the con... trol electrode and anode of said electron discharge devices, an antenna system, means connected between the anode of one of said electron discharge devices and the control electrode of the other of said'electron discharge devices for. controling the operation of said electron discharge devices, and switching means for estab lishing connections between said antenna system and the output circuit of either of said ampliners while simultaneously changing the transmission characteristics of said antenna system.

'4. A signal transmission system comprising in combination a source of substantially-constant high frequency oscillations," an amplifyingsystern for increasing the amplitude of said oscillations, a unit coupled]. to said amplifying system comprisinga pair of electron discharge devices connected into a substantially symmetrical -cir-Z cuit arrangement, a variable condenser interccn- I necting the output circuit ofsaid amplifying sys tem with the input circuit of said unit for varyi ing'the coupling therebetween, oscillatory circuits interconnecting the grid and anode electrodes of said eleciron discharge devices, an antenna system, and means for selectively connecting the 1 output of said amplifying system directly with said-antenna system or through the circuits of said pair of electron discharge devices and simultaneously' fixing thetransmission' characteristics of said antenna system.

5. Asignal transmission system comprising in combination, a source of substantially constant frequency oscillations, three interconnected amplifier stages of which the first stage comprises means for increasing the amplitude of said oscillations and multiplying the frequency thereof, the second stage comprises a shield grid electron discharge device, while the third stage comprises a balanced pair of electron discharge devices having means associated therewith for controlling and maintaining the balanced operation thereof, a variable inductance interconnecting the output circuit of said shield grid electron'discharge device with the input'circuit of said third stage for transferring energy thereto, a variable impedance connected in series with said inductance for adjusting the coupling between the second and third stages, an antenna system and means for selectively connecting said antenna system directly.

with the output circuit of either the second or the third stage while simultaneously fixing the transmission characteristics of said antenna system.

6. A signal transmission system comprising in combination a'source of substantially constant I rendering ineffective that portion of the inducwhich is not operatively associated with the circuits of said electron discharge device, a third amplifying system comprising a pair of discharge devices connectcd'intc a symmetrical circuit arrangernent having means connected therewith for maintaining balanced operation thereof,'a variable impedance device disposed in series with said and the output circuit of saidshield grid electron discharge device for adjusting the coupling between said device and said pair of discharge devices, an antenna system, andmeans for fixing the transmission characteristics of said antenna system while selectivelyconnecting said antenna system directly to the output circuit of either the secondv or the third amplifying system.

I. A signa transmission system comprising in combination a source of substantially constant frequency oscillations, an amplifying system for increasing the amplitude of selected harmonic frequency oscillations .of said substantially consta'nt frequency oscillations, a unit coupled to said amplifying system comprising shield grid electron discharge devices, a second unit comprising a pair of electron discharge devices connected into a symmetrical-balanced circuit arrangement, a variable capacity element connecting the output circuit of the first said unit with the input circuit of the second said unit for adjusting the coupling therebetween, variable means interconnecting the electrodes of said pair of electron discharge devices for maintaining balanced operation of said pair of electron discharge devices, an antenna system and means for fixing the transmission characteristics of said antenna system while selectively connecting said antenna system directly, to either ofsaidunits. j f

8. In a signaling transmission system, a' source of high frequency energy, a'power' amplifier, aradiating circuit, apush-pull power. amplifier, system conne'ctible with said radiating circuit and a connection j'between said first mentioned power amplifier and said push-pull'power; amplifier including a variable capacity element for controlling the coupling between said amplifiers and switching means connected with said radiating circuit f orestablishing connection selectively with the output- 0f said first mentioned power amplifier or the output of said push-pull power ampli- 1 amplifier connected with said source, a radiating system, a push-pull amplifier connectable with lng to vary the coupling between said amplifierswithin the frequency limits covered by said coupling system and switching means connected with said radiating circuit for establishing connection I selectively with the output of said first mentioned franged for selectivelyconnecting the doublet an- .tennaof-said radiation circuit to the output of saidsymmetrical amplification circuit or selectively connecting the parts of said doublet antenna to one side of the output ofsaid unsymmetrical amplification circuit,'the other side of said unsymmetrical amplification circuit being connected-to' ground; I

ILA signaling system comprising a high frequency oscillator, an unsymmetrical amplification circuit connected with said oscillator and having one side thereof connected to ground, a symmetrical amplification circuit connectible witl'rlsaid unsymmetrical amplification circuit, a doublet antenna, switching means for connecting said doublet antenna to the output of said symmetrical amplification circuit said switching means being operative for disconnecting said doublet antenna from said symmetrical amplification *circuit and converting said doublet antenna to a capacity I antenna and establishing connection with the ungrounded side of the output of said unsymmetrical amplification circuit, and means operated by said switching means for disconnecting, said unsymmetrical amplification, circuit from said symmetricalamplification circuit when said unsymmetrical amplification circuit is directly connected'with said converted capacity antenna.

12. Inc, signaling system, a high frequency oscillatdr, an' unsymmetrical'amplification circuit connected with said oscillatoriand having one side thereof connected to ground, a symmetrical amplificationcircuit, a radiation system, switching means for connecting said unsymmetrical amplification circuit with theinput of. said'symmfetrical amplification circuit, andlestablishinjg connection between the output of said symmetrical'aniplification circuit and said radiationcircuit,and

means 1 for disconnecting the aforesaid connections-and modifying the connections of said radi ation circuit and establishing connection between saidmodified radiation'circuit and the ungrounded side of theoutput of said unsymmetrical amplification circuit.

13 In a signaling system, aradiation circuit,

including a doublet antenna, a selector switch having a pair of arms operative over a set of cont acts, a connection between one portion of said doublet antenna and one of said switch arms, a connection between'the other portion, of said doublet antenna and the other of said switch arms, a high frequency oscillator, an unsymmetrical power amplifier connected with said high frequency oscillator, switching means for establishing connection between the output of said unsymmetrical power amplifier and selected 'sets of contacts adjacent said switcharms, a

symmetrical power amplifier coupled with the output of said unsymmetrical power amplifier, a coupling inductance in the output of said symmetrical amplifier, and connections between taps on said coupling inductance and selected contacts adjacent said switch arms whereby movement of said switch arms over said sets of contacts establish-connections between the portions of said doublet antenna and the taps on said coupling inductance, or establish a shunt path between the portions of said doublet antenna and an electrical connection therebetween with one side of said unsymmetrical power amplifier.

14. In a signal transmission system, a radiation circuit comprising a doublet antenna having two independent portions, a pair of switcharms, one of said switch arms being connected with one portion of said doublet antenna, the other of said switch arms being connected with the other portion of doublet antenna, sets of contacts individual to each or" said'switch arms, a high frequency transmission circuit including an unsymmetrical power amplifier and a symmetrical power amplifier, a connection to ground from one side of said unsymmetrical power amplifier means coupling the output of said unsym- ,metrical power amplifier with the-input of symmetrical power amplifier, switching means between one side of the output of said unsymmetrical"power amplifier and selected sets of contacts adjacent each of said switch arms; connections between said sets of contacts whereby the portions of said doublet antenna are electrically connected when said switch arms are moved to positions on the said sets of ccntacts,a coupling inductance in the output'of said symmetrical amplifier, an independent contact individual to each of said switch arms and a tap extending between each of the independent contacts and points on said coupling inductance whereby said antenna portions operate as a doublet in connection with said symmetrical amplifier or as a capacity antenna in connection with said unsymmetrical amplifier.

LOUIS A. GEBHARD. 

